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# How to solve Leetcode 867. Transpose Matrix

Nhut Nguyen
Â·Jun 3, 2022Â·

## Problem statement

Given a 2D integer array `matrix`, return the transpose of `matrix`.

The transpose of a matrix is the matrix flipped over its main diagonal, switching the matrix's row and column indices.

### Example 1

``````Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[1,4,7],[2,5,8],[3,6,9]]
``````

### Example 2

``````Input: matrix = [[1,2,3],[4,5,6]]
Output: [[1,4],[2,5],[3,6]]
``````

### Constraints

• `m == matrix.length`.

• `n == matrix[i].length`.

• `1 <= m, n <= 1000`.

• `1 <= m * n <= 10^5`.

• `-10^9 <= matrix[i][j] <= 10^9`.

## Solution

### Code

``````#include <iostream>
#include <vector>
using namespace std;
vector<vector<int>> transpose(vector<vector<int>>& matrix) {
vector<vector<int>> mt(matrix[0].size(), vector<int>(matrix.size()));
for (int i = 0; i < mt.size(); i++) {
for (int j = 0; j < mt[i].size(); j++) {
mt[i][j] = matrix[j][i];
}
}
return mt;
}
void printResult(vector<vector<int>>& matrix) {
cout << "[";
for (auto row : matrix) {
cout << "[";
for (int m : row) {
cout << m << ",";
}
cout << "]";
}
cout << "]\n";
}
int main() {
vector<vector<int>> matrix = {{1,2,3},{4,5,6},{7,8,9}};
auto result = transpose(matrix);
printResult(result);
matrix = {{1,2,3},{4,5,6}};
result = transpose(matrix);
printResult(result);
}
``````
``````Output:
[[1,4,7,][2,5,8,][3,6,9,]]
[[1,4,][2,5,][3,6,]]
``````

### Complexity

• Runtime: `O(m*n)`, where `m = matrix.length`, `n = matrix[i].length`.

• Extra space: `O(1)`.

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